Business Segments (Statement of Operations and Total Assets by Reportable Segment) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 90,696	$ 84,955	$ 77,191
Noninterest income	65,214	52,764	48,473
Total income	155,910	137,719	125,664
Provision for loan losses	2,700	4,700	6,000
Depreciation and amortization expense	3,941	4,125	4,174
Other noninterest expenses	98,397	86,248	81,137
Total noninterest expense	102,338	90,373	85,311
Income before income taxes	50,872	42,646	34,353
Income tax expense (benefit)	15,798	12,922	10,302
Net income	35,074	29,724	24,051
Total assets at period end	3,071,884	3,064,098	2,909,525
Expenditures for long-lived assets	5,110	3,644	1,683
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	79,505	75,967	73,788
Noninterest income	31,727	21,806	19,770
Total income	111,232	97,773	93,558
Provision for loan losses	2,700	4,700	6,000
Depreciation and amortization expense	2,384	2,512	2,376
Other noninterest expenses	62,963	55,543	51,002
Total noninterest expense	65,347	58,055	53,378
Income before income taxes	43,185	35,018	34,180
Income tax expense (benefit)	14,670	11,781	11,821
Net income	28,515	23,237	22,359
Total assets at period end	2,436,280	2,257,326	2,095,515
Expenditures for long-lived assets	4,082	2,982	994
Wealth Management Service [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	17	(1)	(47)
Noninterest income	29,640	28,306	26,392
Total income	29,657	28,305	26,345
Provision for loan losses	0	0	0
Depreciation and amortization expense	1,272	1,330	1,461
Other noninterest expenses	19,584	19,041	18,751
Total noninterest expense	20,856	20,371	20,212
Income before income taxes	8,801	7,934	6,133
Income tax expense (benefit)	3,296	2,957	2,296
Net income	5,505	4,977	3,837
Total assets at period end	51,730	51,104	51,164
Expenditures for long-lived assets	877	493	176
Corporate [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	11,174	8,989	3,450
Noninterest income	3,847	2,652	2,311
Total income	15,021	11,641	5,761
Provision for loan losses	0	0	0
Depreciation and amortization expense	285	283	337
Other noninterest expenses	15,850	11,664	11,384
Total noninterest expense	16,135	11,947	11,721
Income before income taxes	(1,114)	(306)	(5,960)
Income tax expense (benefit)	(2,168)	(1,816)	(3,815)
Net income	1,054	1,510	(2,145)
Total assets at period end	583,874	755,668	762,846
Expenditures for long-lived assets	$ 151	$ 169	$ 513